This disclosure generally relates to a pressure control valve. In particular, this disclosure is directed to an electrically operated valve to control the level of vapor pressure in a fuel tank of a vehicle.
It is believed that prior to legislation requiring vehicles to store hydrocarbon vapors that are generated when refueling a vehicle, a simple orifice structure was used to maintain a positive pressure in a fuel tank to retard vapor generation. It is believed that such orifice structures could no longer be used with the advent of requirements controlling on-board refueling. It is believed that, on some vehicles, the orifice structure was simply deleted, and on other vehicles, the orifice structure was replaced with a diaphragm-actuated pressure relief valve. It is believed that these diaphragm-actuated valves suffer from a number of disadvantages including that the calibration (i.e., pressure blow-off level) changes with temperature and age.
It is believed that it is necessary on some vehicles to maintain an elevated pressure in the fuel tank to suppress the rate of fuel vapor generation and to minimize hydrocarbon emissions to the atmosphere. It is believed that under hot ambient temperature conditions or when the fuel is agitated, e.g., when a vehicle is operated on a bumpy road, the amount of fuel vapor generated can exceed the amount of fuel vapor that can be purged by the engine. It is believed that a carbon canister can become hydrocarbon saturated if these conditions occur and are maintained for an extended period. It is believed that such a hydrocarbon saturated carbon canister is unable to absorb the additional fuel vapors that occur during vehicle refueling, and that hydrocarbon vapors are released into the atmosphere. A legislated standard has been set for the permissible level of free hydrocarbons that may be released. A so-called xe2x80x9cshed testxe2x80x9d is used to measure the emission of the free hydrocarbons for determining compliance with the legislative standard.
It is believed that there is needed to provide a valve that overcomes the drawbacks of orifice structures and diaphragm-actuated pressure relief valves.
The present invention provides a valve structure that comprises a housing, a valve, a first resilient element, and a second resilient element. The housing includes a first fluid communication path between a first port and a second port. The valve is movable with respect to the housing, and includes a first valve element and a second valve element. The first valve element includes a second fluid communication path, a first seal, and a second seal. The second fluid communication path provides restricted fluid flow between the first and second ports. The first seal engages the housing. The second valve element is positionable between first and second arrangements with respect to the first valve element. The first arrangement of the second valve is spaced from the second seal, and the second arrangement of the second valve engages the second seal. The first resilient element extends between the housing and the first valve element, and the second resilient element extends between the first and second valve elements.
The present invention also provides a valve structure that comprises a housing and a valve. The housing includes a first communication path between a first port and a second port. The valve is movable with respect to the housing between a first configuration, a second configuration, and an intermediate configuration between the first and second configurations. The first configuration permits substantially unrestricted fluid flow between the first and second ports. The second configuration substantially prevents fluid flow between the first and second ports. The intermediate configuration provides restricted fluid flow between the first and second ports. The valve includes a first valve element and a second valve element. The first valve element includes a second fluid communication path, a first seal, and a second seal. The second fluid communication path provides the restricted flow between the first and second ports. The first seal engages the housing in the second and intermediate configurations. A second valve element is positionable between first and second arrangements with respect to the first valve element. The first arrangement of the second valve is spaced from the second seal in the intermediate configuration, and the second arrangement of the second valve engages the second seal in the second configuration.
The present invention further provides a valve for controlling fuel vapor pressure in a fuel tank. The valve comprises a housing, an actuator, a first valve element, a second valve element, a first resilient element, and a second resilient element. The housing includes an inlet port and an outlet port. The actuator includes a stator and an armature. The stator is fixed with respect to the housing, and the armature is displaceable along an axis with respect to the stator. The first valve element includes a first disk. The first valve element is fixed with respect to the armature and displaceable along the axis with respect to the housing. The second valve element includes a second disk and at least one aperture, which penetrates the second disk and extends generally parallel to the axis. The second valve element is displaceable along the axis with respect to the housing and the first valve element. The first resilient element extends between the housing and the second valve element and opposes an actuating force of the actuator. The second resilient element extends between the first and second valve elements and opposes displacement of the second body toward the first body. There are a plurality of configurations of the first and second valve elements with respect to the housing. A first configuration permits substantially unrestricted fluid flow from the inlet port to the outlet port. In the first configuration, the second valve element is spaced from the housing such that fluid communication is permitted between the inlet and outlet ports through a gap between the second disk and the housing. Also in the first configuration, the first valve element is spaced from the second valve element such that fluid communication is permitted between the inlet and outlet ports through the at least one aperture penetrating the second disk. A second configuration substantially prevents fluid flow from the inlet port to the outlet port. In the second configuration, the second valve element engages the first valve element such that fluid communication between the inlet and outlet ports is prevented through the at least one aperture penetrating the second disk. A third configuration provides restricted fluid flow from the inlet port to the outlet port. In the third configuration, the second valve element engages the housing such that the gap is closed. Also in the third configuration, the first valve element is spaced from the second valve element such that fluid communication is permitted between the inlet and outlet ports through the at least one aperture penetrating the second disk.